The present invention relates to a method and a device for filling pressure gas containers.
The invention relates in particular to a method and a device for filling containers such as pressurized gas cylinders or tanks.
The filling of high pressure vessels, for example on board vehicles running on hydrogen gas, must be carried out as quickly as possible to decrease the vehicle immobilization time.
The final service pressures of these vessels or tanks are generally between 350 and about 700 bar.
Due to the virtually adiabatic nature of the compression of the gas in the tanks and the high final pressures, the gas temperature in the tanks rises rapidly and is liable to damage the composite structure of the tanks.
It is therefore important to limit this temperature rise to the design temperature of the tank, that is a maximum allowable temperature (generally about 85° C.).
One known solution for controlling this filling temperature consists in interrupting the filling in case of overheating.
Another solution consists in controlling the filling rate so that it remains lower than a flow rate that could cause excessive temperature rise.
These two known methods require control of the flow rate of gas fed to the tank and therefore the use of a high pressure control valve, which is very expensive.
In these known solutions, a first embodiment consists in controlling the gas flow rate directly upstream or downstream of the control valve.
A second embodiment not using a flowmeter consists in controlling the pressure rise rate downstream of the control valve (the pressure rise rate being the derivative of the pressure downstream of the valve with respect to time).
The filling is generally carried out from a pressure gas reserve. Thus, in these prior art solutions, as the pressure increases in the tank to be filled (downstream of the valve), the pressure in the source decreases. The dynamic control range of the valve is therefore very important because it must control a flow rate or a constant temperature rise, whereas neither the pressure upstream of the valve nor the pressure downstream of the valve is constant. The valve control loops therefore require a relatively long adjustment time and a control valve having a broad opening/closing dynamic range. A poor adjustment of the valve control loop either prevents reaching the target pressure at the end of filling or causes overheating of the tank if the target pressure is reached before the planned filling time.
It is an object of the invention to propose a method for filling a pressure gas container that overcomes all or part of the drawbacks of the prior art.